Prepared to think small? You could be a backyard naturalist

A grazier from southern New South Wales wrote, telling of a dust storm that began at five in the evening, was still dense at dark, and probably long after.

Dust is topsoil. As a kid, the woman sometimes had to ride her pony home from school sticking to the fenceline - dust obscured all else.

"Also, I have seen a brown-snake track across the drive, grass-snake track near the house, marks of a goanna near the stable," she wrote.

Blackbirds are often the first introduced bird to appear in a disturbed wild environment - when you build a house in the bush, for example - to compete with native birds.

This grazier steals their eggs, hard-boils them and returns them to the nest. The bird then sits and sits. If you destroy eggs, the bird lays again immediately. I approve her action yet enjoy waking to blackbird song in the city.");document.write("

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Guess which introduced species has most damaged this continent? Hint: it is not the rabbit.

The grazier said that rain would be useless until autumn, because it would only germinate weed species such as Paterson's curse. Thinking of dams and tanks, I found this to be strange, but know little of the world in which she lives. Do we all live in different worlds?

In the city, it is useless to inspect the ground for goanna tracks. We cannot lean out of the window to view brolgas. But a mentor, Patrick Honan, keeper of invertebrates at the zoo, says that there are more than a thousand native animal species living in Melbourne back yards.

Native birds, mammals (for example, possums), reptiles (for example, skinks) and frogs account for very few. Nearly all are invertebrates. We can, if prepared to think small, be naturalists without leaving home. Start by lifting a rock in the garden or putting a spider, and its web, under a strong magnifying glass.

We are reducing the number of invertebrate species by denying them food-plants, and paving ever more square metres for cars, outdoor living, wheelchairs, high-heels, etcetera, but many inverts will never be overcome. In a city flat, examine foliage on the window-ledge geraniums, the mites in the carpet, the webs in the corners, mozzies or perhaps ants.

On a quarter-acre block, some inverts inhabit trees, some never leave the ground (trapdoor spiders), others live in burrows (mole crickets) or use ground and trees - cicadas. Many are nocturnal - orb-weaver spiders and emperor gum moths. They kill, and live on each other. To demonstrate that we "need" invertebrates is easy, but human-centric - they are a necessary part of the whole.

Plant local, native species for them. Don't use insecticides (squash pests, instead). Be prepared to live with minor pests. Try to be rid of the "neat garden" mind-set, have an unkept garden with at least some native grasses, forbs, shrubs, trees.

I still admire park-like grazing properties dotted with grand old trees, the white homestead on its hill, all as though designed by Capability Brown. But what happens when those native trees die?

Honan says that Tim New, zoologist at LaTrobe University, takes students into the bush to find a leaf that has not been nibbled by an insect and that it may take 20 students at least 20 minutes to find one such leaf.

He postulates a theory that our many eucalypts have specified, in part, because of insect attack.

A single eucalyptus tree, fed to the back teeth with insect damage, evolves chemical nasties in its leaves that insects cannot tolerate. It flourishes, seeds, develops the new characteristics with each generation, and gradually becomes a clearly individual species with no major predator.

In response, (it takes awhile) an insect may evolve that is able to tolerate that particular set of chemicals. It passes these genes to its progeny and they breed like mad on a virgin food source, perhaps as a new insect species, which may use those chemical nasties to make its own body unpalatable to predators.